Electrocoagulation - Overview
of the Technology
Coagulation is a critical
physio-chemical operation used in water
treatment. This is a process used to cause
the destabilization and subsequent aggregation
of smaller particles into larger complexes.
Water contaminants such as ions (heavy metals)
and colloids (organic and inorganic) are
primarily held in solution by electrical
charges. Colloidal systems could be destabilized
by the addition of ions of the charge opposite
to that of the colloid. The destabilized
colloids can then aggregate and subsequently
be separated from the wastewater.
Coagulation can be achieved
by both the chemical or electrical means.
Chemical coagulation has been used for decades
to destabilize suspensions and to effect
precipitation of soluble species and other
pollutants from aqueous streams. Alum, lime
and polymers are some of the chemical coagulants
used. These processes, however, tend to
generate large volumes of sludge with high
bound water content which can be difficult
to separate and dewater. The processes also
tend to increase the total dissolved solids
content of the effluent, making it unacceptable
for reuse within industrial applications.
Other aspects of chemical coagulation are
also becoming increasingly less acceptable.
The disposal cost of the large volumes of
sludge (generally of fairly high hazardous
waste category), the cost of the chemicals
required to achieve coagulation and the
environmental issues associated with the
process are critical problems in many industries.
Electrocoagulation, the passing
of the electrical current through water,
has proven very effective in the removal
of contaminants from water. Although the
electrocoagulation mechanism resembles the
chemical coagulation - the cationic species
being responsible for the neutralization
of surface charges - in many ways it is
very different. Electrocoagulation is a
process of destabilizing suspended, emulsified
or dissolved contaminants in an aqueous
medium by introducing electrical current
into the medium. The electrical current
provides the electromotive force causing
the chemical reactions.
Several distinct electrochemical
processes occur during the electrocoagulation
Seeding resulting from the
anode reduction of metal ions that become
new centers for larger, stable, insoluble
Emulsion breaking resulting
from oxygen and hydrogen ions reacting with
emulsified substances and forming water
Halogen completing - as the
metal ions bind themselves to halogens resulting
in formation of large insoluble complexes
and isolating pesticides, herbicides, chlorinated
Bleaching by oxygen species
produced in the reaction chamber and providing
oxidisation of chemical substances and also
reducing bio-hazards through oxidisation
of bacteria, viruses, etc..
Electron flooding of the water
affects the polarity of water, allowing
colloidal materials to precipitate.
The electrons create osmotic
pressure rupturing cell walls of bacteria,
cysts, and viruses. Oxidation and reduction
reactions are forced to their natural end
point. Electrocoagulation can speed up the
natural processes occurring in wet chemistry
Electrocoagulation induced pH typically
shifts towards neutral. The principal cathodic
reaction is the reduction of hydrogen ions
to hydrogen gas (2H+ + 2e- = H2). The principal
anodic reaction is the release of metal
ions into solution (eg. 3Al = Al3+ + 3e-).
The anodes are sacrificed during the process.
The wastewater passes through
a chamber with the cathodes and anodes.
The electrical current is introduced via
parallel plates constructed of metals selected
to optimise the removal process. The two
most common plate materials are iron and
aluminium. In accordance with the Faraday's
Law, the metal electrodes are sacrificed
and slowly dissolve into the liquid medium.
The metal ions tend to form metal oxides
that electromechanically attract the destabilized
contaminants. After the treated wastewater
leaves the electrocoagulation chamber, the
destabilized colloids are allowed to flocculate
and then separated in an integrated system.
The sludge can be further de-watered using
a filter press, settling pond, or other
Removes heavy metals;
Removes suspended and colloidal
Destabilizes oil and other
Removes fats, oils and grease;
Removes complex organics;
and Destroys and reduces bacteria, viruses
Treats multiple contaminants;
Capital cost significantly
less than conservative technologies;
Operating cost significantly
less than conservative technologies;
Low power requirements;
Minimal operator attention;
Consistent and reliable results.
contacct ForeverPure for detailed information.